Heat insulating casing

ABSTRACT

This invention relates to the compacting of powdered-metal charges by fluid-pressure application in an autoclave, while said charge is at elevated temperature to eliminate the need for heating in the autoclave. In accordance with the invention, heat dissipation from the charge is minimized by the use of a removable heat-insulating casing that covers the charge after it has been heated externally of the autoclave and until compacting has been completed in the autoclave.

United States Patent Inventor Charles Benjamin Boyer Columbus, Ohio Appl. No. 772,681 Filed Nov. 1, 1968 Patented Aug. 17, 1971 Assignee Crucible Inc.

Pittsburgh, Pa.

HEAT INSULATING CASING 10 Claims, 3 Drawing Figs.

US. Cl. 18/5 H, 18/16 R, 18/17 A, 29/420, 29/421, 75/214, 75/226, 264/111, 264/125 Int. Cl. 132213/12 Field Search 18/5 1-1, 16 R, 16.5, 16.7, 17 A;75/2l4,226;264/l11,125; 29/420, 421

References Cited UNITED STATES PATENTS 10/1938 Reid l8/17A 3/1965 Loomis et a1. 18/5 1'1 4/1966 18/5 H X 5/1966 18/5 H 6/1966 75/226 X 1/1969 18/5 H Primary Examiner-William S. Lawson Attorney-Clair X. Mullen, Jr.

autoclave.

. nan INSULATINGCASING It is well known that by :the useof powdered metallurgy techniques it is possible to produce metal articles, such as high alloy tool steel articles, of fine grain size and homogeneous microstructure The conventional practice for producing articles ofthis type is to place a charge of powdered metal of,

, this type, to achieve adequate density during compacting,

which typically must be about 95 percent or greater, it is critical that the powderedmetal charge not be permitted to cool below the temperature at which upon pressure application the required compact density will be achieve'd.jSince the chargev filled container must be heated to compacting temperature ina furnace, removed from the furnace when the required temperature has been achieved, and transported to an autoclave for compacting, substantial heat loss can result during this sequence. If, to counteract the heat loss, the charge is heated to temperatures far in excess of that required for compacting, such high temperatures will cause undesirable metallurgical changes, such as'carbide and sulfide growth and agglomeration, Particularly in the case of tool steel articles, agglomeration of carbides and sulfides results in a lessening of the cutting life of any tools made from such material. Alternately, if the charge is supplied with supplemental heat while inthe autoclave, this adds substantially to the size, cost and complexity of the autoclave apparatus as well as to the time that the charge remains in the autoclave.

' It is accordingly the primary object of the present invention to provide for the high-temperature compacting of powdered metal charges in an autoclave wherein heat loss is minimized during transport of the charge from the heating furnace to the autoclave, and during the time in the autoclave prior to compacting. r

' A more particular object of the invention is to provide a heat-insulating casing covering the powdered-metal filled container during transport thereof fro rnjthe heating furnace to the autoclave, whereby supplemental heating of the charge within the autoclave may be eliminated.

, Yet another object of the invention is to provide a heat-insulating casing for use in preventing heat loss from a powderedmetal filled container, said heat-insulating casing being adapted to permit unitary removal of the container and casing from the furnace and transport to the autoclave.

Another. related object of the invention is to provide a casing that will insulate the powder-filled container against heat loss and will also protect the interior of the autoclave from damage by the high temperatures andscale of the container.

These and other objects of the invention, as well as a complete understanding thereof, will be obtained from the followingdescription and drawings, in which:

FIG. '1 is an elevational view of a typical cylindrical container for a powdered-metal charge, with parts broken away to show the powdered metal therein;

FIG. 2 is an elevational view of the container of FIG. I with the heat-insulating casing, with portions of the casing broken away to show the heat-insulating material therein, in accordance with the present invention positioned thereover; and

FIG. 3 is an elevational view in partial, vertical section of the container and casing of FIG'. 2 positioned in an autoclave for compacting, with portions of the container and casing broken away toshow the heat-insulating material therein.

Broadly, the present invention comprises a heat-insulating casing having an interior confonning substantially to the configuration of the container of powdered metal to be compacted. When the charge has reached the required compact- ,ing temperature within a furnace locatedexterior' of the autoclave, it is separated from the furnace and the heat-insulat ing casing of the invention is lowered, as by the use of an overhead crane, to cover the container. Means are provided near the bottom of the casing for connecting the same to a base or pedestal upon which thecontainer rests during heating in the furnace. The connection, is such as to permit the container, base and heat-insulating casing to be removed, from,the furnace as a unit by the use of an overhead crane and transported thereby to an autoclave. For this purpose the connection may comprise a pin that is passed through the casing and into the base or alternately a pin that is fixed in the base and locks into a slot in the casing. The unit is then positioned in the autoclave for compacting. By this arrangement, the time between the completion 6f heating and the beginning of compacting is greatly. minimized and, in addition, the heat-insulating casing minimizes heat loss from the charge during transport and prior to compacting in the autoclave; Preferably, the heat-insulating casing comprises an inner shell that conforms substantially to the configuration of the powder-filled container and an outer shell that is generally cylindrical to conform to the generally cylindrical autoclave. The outside diameter of the casing should be only slightly less than the inside diameter of the autoclave to further minimize heat loss while the unit is within the" autoclave awaiting the application of fluid pressure for compacting. The inner and outershells are in spaced-apart relation to create a space therebetween that is filled with a heat-insulating material, such as zirconia.

With reference to FIGS. 1 through} of the drawings, there is shown a cylindrical container 10, which may be constructed from a mild steel, having an upwardly extending stem 12. As best shown in FIG. 1, the; container interioris filled with a charge of powdered metal 14 to be compacted. Stem 12 of the container permits connection to a means, such as a pump, for evacuating the container interiorafter it has been filled with the powdered-metal charge. The container may typically have a 10-inch diameter with a length of 47 inch.

During heating, the container is supported in an upright position, as shown in the figures, on a base or pedestal {6. The top or supporting surface of the pedestal is provided with a refractory pad I8. A drilling 20, which is normal to the axis of the base 16, is provided to accommodate a pin connection used for connecting the heat insuIating casing to the container 10 and base. This casing, which is indicated generally as 22, is best shown in FIG. 2. The casing 22 comprises an outer shell 24 of generally cylindrical configuration and an inner shell 26 having dimensions slightly greater than but confonning with those of the container 10. In this manner, the casing 22 may be placed over the container, as by the use of an overhead crane (not shown), to cover said container as shown in FIG. 2 of the drawings. To permit lilting and transport of the casing 22, a crane hook 28 is provided on the top thereof. Near the bottom of the casing, there are provided axially aligned openings in the shells 24 and 26 that are aligned with drilling 20 in the base 16 upon positioning of the casing over the container and base. With the casing in this position, as shown in FIG. 2, a pin 32 is inserted through the openings 30,and drilling 20. This serves to connect the casing with the hue 16, and upon lifting v of the casing, as by connection of a crane hook at 28, the container 10, base 16 and heat-insulating casing 22 may be lifted as a unit from the furnace and repositioned as a unit in an autoclave. As an alternate arrangement, the pin may be fixed within the base and thus extend therefrom in opposite directions as stationary lugs. Slots are provided inthe bottom of the easing into which the pin ends" or lugs may be locked as by taming the casing about its vertical axis upon positioning of the lugs within the slots. The unitary positioning of the container, base and heat-insulating casing within an autoclave is shown in FIG. 3 of the drawings. The autoclave, a portion of which is shown in FIG. .3 and designated generally as 33, has a cylindrical interior 34 that is lined removable stacked cylindrical inserts 36. The inserts 36 act as an armor to protect the autoclave interior. These inserts may be of various diameters depending upon the diameter of the heat-insulating casing to be positioned in the autoclave. As pointed out hereinabove,

cation of fluid pressure for compacting. Heat loss is further W minimized by the space between the shells 24 and 26 of the casing being filled with a heat-insulating material 38, which may be a refractory or insulating oxide material, such as zirconia, magnesia or silica. Because of the high temperatures involved, the shells 24 and 26 of the casing are preferably constructed from a heat-resistant material, such as stainless steel.

Although various embodiments of the invention have been shown and described herein, it is obvious that other adaptations and modifications may be made by those skilled in the art without departing from the scope and spirit of the appended claims.

I claim:

1. In combination with a container having therein a powdered-metal charge to be compacted by fluid-pressure application while at elevated temperature, a removable heat-insulating casing for minimizing cooling of said powdered-metal charge after said charge has been heated in a furnace to compacting temperature and prior to compacting.

2. A heat-insulating casing as recited in claim 1 having an interior conforming substantially to the configuration of said container and covering a major portion thereof.

3. A heat-insulating casing as recited in claim 1 having means for removably connecting said casing to a portable base upon which said container is supported.

4. The apparatus of claim 3 wherein said means for removably connecting said casing to said base includes a pin that extends through said casing and into said base.

5. A heat-insulating casing as recited in claim 1 having an inner shell and an outer shell in spaced-apart relation.

6. A heat-insulating casing as recited in claim 5 having a heat-insulating material between said inner and outer shells.

7. A heat-insulating casing as recited in claim 6 wherein said heat-insulating material is selected from the group consisting of zirconia, magnesia and silica.

8. In combination with a container having therein a powdered-metal charge to be compacted by fluid-pressure application while at elevated temperature, a removable heat-insulating casing for minimizing cooling of said powdered-metal charge after heating to compacting temperature and prior to compacting, said casing comprising an inner shell and an outer shell in spaced-apart relation, said inner shell conforming substantially to the configuration of said container and covering a major portion thereof, a heat-insulating material between said inner and outer shells, and means for removably connecting said casing to a portable base upon which said container is supported.

9. The casing of claim 8 wherein said means for removably connecting said casing to said base includes a pin that extends through said inner and outer shells and into said base.

10. A method for producing a compact by fluid-pressure compacting a powdered-metal charge at elevated temperature within a container, comprising providing a container having therein a charge of powdered metal to be compacted, heating said container and charge in a furnace to an elevated temperature not less than a selected compacting temperature at which UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,599,2 1 Dated August 17, 1971 Inventor(s) Charles Benjamin Boyer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 23, after "autoc lave", insert --interior,

which reduces the void volume within the autoclave-.

Column 2, line 38, change "inch" (second occurrence) to --inches--,

Signed and sealed this L th day of January 1972.

(SEAL) Attest:

EDWARD MF'LETGHER, JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents OHM PO IOSO (10-69) USCOMM-DC GOING-P69 Q u 5 GOVERNMENT PRINTING OFFICE 1969 (1J65-]J4 

2. A heat-insulating casing as recited in claim 1 having an interior conforming substantially to the configuration of said container and covering a major portion thereof.
 3. A heat-insulating casing as recited in claim 1 having means for removably connecting said casing to a portable base upon which said container is supported.
 4. The apparatus of claim 3 wherein said means for removably connecting said casing to said base includes a pin that extends through said casing and into said base.
 5. A heat-insulating casing as recited in claim 1 having an inner shell and an outer shell in spaced-apart relation.
 6. A heat-insulating casing as recited in claim 5 having a heat-insulating material between said inner and ouTer shells.
 7. A heat-insulating casing as recited in claim 6 wherein said heat-insulating material is selected from the group consisting of zirconia, magnesia and silica.
 8. In combination with a container having therein a powdered-metal charge to be compacted by fluid-pressure application while at elevated temperature, a removable heat-insulating casing for minimizing cooling of said powdered-metal charge after heating to compacting temperature and prior to compacting, said casing comprising an inner shell and an outer shell in spaced-apart relation, said inner shell conforming substantially to the configuration of said container and covering a major portion thereof, a heat-insulating material between said inner and outer shells, and means for removably connecting said casing to a portable base upon which said container is supported.
 9. The casing of claim 8 wherein said means for removably connecting said casing to said base includes a pin that extends through said inner and outer shells and into said base.
 10. A method for producing a compact by fluid-pressure compacting a powdered-metal charge at elevated temperature within a container, comprising providing a container having therein a charge of powdered metal to be compacted, heating said container and charge in a furnace to an elevated temperature not less than a selected compacting temperature at which said charge is to be compacted, covering said container with a removable, heat-insulating casing, removing said casing and container from said furnace as a unit and placing said unit within a fluid-pressure vessel, and compacting said powdered-metal charge by the application of fluid pressure before said charge cools to a temperature below said selected compacting temperature. 